DESCRIPTION: (Applicant's Abstract) Dopamine (DA) activity is strongly implicated in the reinforcing properties of drugs of abuse. The reinforcing properties of such drugs appear to result from pharmacological activation of DA substrates which mediate natural reinforcement processes. Critical gaps exist in the experimental literature, however, regarding the precise function(s) of DA in reinforcement, particularly within specific brain target sites. Humans acquire associations between A) their behaviors and reward events (response-reward) and B) between environmental stimuli and rewards (CS-reward); rats acquire similar associations. Is DA involved in the acquisition of response-reward, CS-reward, and/or stimulus-response associations during reinforcement? What is the precise role of DA within these associative mechanisms at different brain target sites? In light of recent information from single-unit and dialysis studies of DA activity in behaving animals, the studies in this application examine the precise nature of DA's role in the acquisition of CS-reward associations, within three brain target structures, the nucleus accumbens, caudate, and prefrontal cortex. The studies will examine, for each brain target site, whether DA disruption of CS-reward learning is dependent upon the intensity of the CS, the time interval between CS and reward, and whether DA disruptions impair aversive as well as appetitive CS-outcome associations under varying intensities of the aversive outcome.